Scientists Explain How Supermassive Black Holes Keep Galaxies Turned Off

Posted: May 26 2016, 1:01am CDT | by , Updated: May 27 2016, 8:20am CDT, in News | Latest Science News


Scientists Explain How Supermassive Black Holes Keep Galaxies Turned Off
An artist's impression red geyser Akira. Credit: Kavli IPMU

Giant black holes are turning a huge number of lively galaxies into cosmic graveyards.

Over the last few billion years, a strange phenomena is causing to turn a huge number of lively galaxies,capable of producing stars, into a place devoid of young stars.

Now, an international team of researchers have found an explanation for this malfunctioning and they believe that it’s the most logical one and worthy to solve this longstanding mystery. These are many colorful spiral galaxies in the universe that are full of star-forming material and were actively giving birth to new stars initially but gradually the process stopped and those galaxies could not produce fresh stars any longer. It was like something has switched them off.

“The galaxies have the necessary ingredients for forming new stars but they are not doing it -- why?” Renbin Yan professor of physics and astronomy from University of Kentucky said.

Researchers have discovered a surprisingly common phenomenon in the galaxies called “red geysers” which is likely refraining star formation.

Red geysers are older galaxies that harbor low-energy black holes in their cores. These black holes are capable of driving intense stellar winds. Intense winds heat up the gas moving around in the galaxies and prevent it from cooling and converting into stars. The process is called galactic warming.

“Stars form from the gas, but in many galaxies stars were found not to form despite an abundance of gas. It was like having deserts in densely clouded regions,” said lead author Dr Edmond Cheung from University of Tokyo. “We knew quiescent galaxies needed some way to suppress star formation and now we think the red geysers phenomenon may represent how typical quiescent galaxies maintain their quiescence.”

Thanks to the large-scale survey of galaxies, called Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), researchers were able to identify and explain the phenomena. 

MaNGA is the first digital survey where 10,000 nearby galaxies were examined in order to understand their life cycle. Unlike previous surveys, it not only mapped the center of the galaxies where giant black holes lie but also the outer edges of the galaxies, which in turn, enabled researchers to spot minute changes happing in the galaxies, leading them to the discovery of red geysers.

“The discovery was made possible by the amazing power of the ongoing MaNGA galaxy survey,” said Dr Kevin Bundy, from the University of Tokyo. “The survey allowed us to observe galaxies in three dimensions, by mapping not only how they appear on the sky, but also how their stars and gas move inside them.”

Researchers have taken a galaxy named Akira as a prototype sample and closely looked at the galaxy to understand the wind driving mechanism. Akira’s galactic nucleolus is powered by a supermassive black hole which is strong enough to generate wind that can blow fast and suppress the star formation. The powerful wind is exactly the reason why Akira has become a red geyser galaxy.

“Stars form from the gas, a bit like drops of rain condense from the water vapor. And in both cases one needs the gas to cool down, for condensation to occur,” said co-author Dr Michele Cappellari from Oxford University. “When we modeled the motion of gas in the red geysers, we found that the gas was being pushed away from the galaxy center and escaping the galaxy gravitational pull.” In other words, these giant black holes are turning gas rich galaxies into cosmic graveyards.”

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Hira Bashir covers daily affairs around the world.




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